//Code by Patcas Csaba

#include <vector>
#include <string> 
#include <set> 
#include <map> 
#include <queue> 
#include <bitset> 
#include <stack>
#include <list>

#include <numeric> 
#include <algorithm> 

#include <cstdio>
#include <fstream>
#include <iostream> 
#include <sstream> 
#include <iomanip>

#include <cctype>
#include <cmath> 
#include <ctime>
#include <cassert>

using namespace std;

#define LL long long
#define PII pair <int, int>
#define VB vector <bool>
#define VI vector <int>
#define VD vector <double>
#define VS vector <string>
#define VPII vector <pair <int, int> >
#define VVI vector < VI >
#define VVB vector < VB >

#define FORN(i, n) for(int i = 0; i < (n); ++i)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define REPEAT do{ 
#define UNTIL(x) }while(!(x)); 

#define SZ size()
#define BG begin() 
#define EN end() 
#define CL clear()
#define X first
#define Y second
#define RS resize
#define PB push_back
#define MP make_pair
#define ALL(x) x.begin(), x.end()

#define in_file "a.in"
#define out_file "a.out"
#define INF 2000000000

int n;
VVI a, sum;

int subSum(int i1, int j1, int i2, int j2)
{
	if (i1 > i2 || j1 > j2)  return 0;
	return sum[i2][j2] + sum[i1 - 1][j1 - 1] - sum[i1 - 1][j2] - sum[i2][j1 - 1];
}

int main()
{
	//Read data
	//freopen(in_file, "r", stdin);
	//freopen(out_file, "w", stdout);
	
	cin >> n;
	a.RS(n + 1, VI(n + 1)), sum.RS(n + 1, VI(n + 1));
	FOR(i, 1, n)
		FOR(j, 1, n) 
		{
			cin >> a[i][j];
			sum[i][j] = sum[i - 1][j] + sum[i][j - 1] - sum[i - 1][j - 1] + a[i][j];
		}

	//Solve
	int best = -INF;
	FOR(i1, 1, n)
		FOR(j1, 1, n)
			FOR(i2, i1, n)
				FOR(j2, j1, n)
				{
					int borderSum = subSum(i1, j1, i2, j2) - subSum(i1 + 1, j1 + 1, i2 - 1, j2 - 1);
					best = max(best, borderSum);
				}
	//Write data
	cout << best;

	return 0;
}